The present invention relates to foundation piles and similar load carrying structural elements.
A pile and/or load carrying similar structural element design advancing the present art is required to address all the following engineering characteristics:
a) Components that don""t rust, corrode, or decompose when exposed to fresh water and/or sea water and/or sewage and/or water-borne creatures, plants, bugs or other things that like to eat,
b) Does not require getting ready-mix concrete to the job-site,
c) Ease of transport to job-site,
d) Ease of handling and rigging, in marine and other similar applications, structural element sections, such as, but not limited to, piles, should float,
e) Requires no new expensive handling and/or pile driving equipment,
f) Quick field jointing of structural element sections, such as, but not limited to, piles,
g) Structural element sections, such as, but not limited to, piles, design and construction by components certified and in use by state agencies and approved for use by Federal Agencies,
h) Allows the use of existing engineering design codes, addresses pertinent engineering design consensus standards and specifications,
i) provides a high xe2x80x9ccoefficient of skin-frictionxe2x80x9d,
j) the pile designer should be able to tailor the pile""s xe2x80x9ccoefficient of skin-frictionxe2x80x9d to the expected soil matrix the pile is to be placed in,
k) the structural element sections, such as, but not limited to, piles, should be fire resistant, through application of a xe2x80x9cwearing surfacexe2x80x9d
l) the structural element sections, such as, but not limited to, piles, should resist impact damage, the pile design should allow for expected impact loads associated with transport, placement, installation and intended use, plus safety factor, through application of a xe2x80x9cwearing surfacexe2x80x9d.
m) the structural element sections, such as, but not limited to, piles, design should allow for inspection in-situ.
The present art of marine pile design has been limited to that constructed of steel, wood, or metal reinforcement concrete due to economic and engineering reasons. Maintenance costs due to corrosion of metal components and attack of boring marine animals on wood component have resulted in numerous attempts to address the shortcomings of the present art of marine pile design.
Grosse and Fehr U.S. Pat. No. 3,939,665 (Feb. 24, 1976) describe xe2x80x9c. . . the application of a coating of a corrosion resistant covering consisting of an outer shield of stiff plastic . . . xe2x80x9d protecting an existing, already-in-place, metal H-pile. The Grosse and Fehr U.S. Pat. No. 3,939,665 xe2x80x9c. . . relates to the protection of metal piles from corrosion in underwater and semi-underwater environments.xe2x80x9d Grosse and Fehr U.S. 3,939,665 references Fox, U.S. Pat. No. 1,013,758 (Jan, 2, 1912), and Drusbel et al., U.S. Pat. No. 2,874,548 (Feb. 24, 1959), and Liddell, U.S. Pat. No. 3,321,924 (May 30, 1967) and finally Wiswell, U.S. Pat. No. 3,370,998 and states xe2x80x9c(S)uch prior disclosures and practices, while effective to various extents to apply corrosion resisting coatings to piling in general, have not been notably successfully in applying corrosion resistant coatings to H or I-type metal piling or other irregularly shaped piling. It has in particular proven very difficult, and in many cases substantially impossible to obtain a good interfit which is effective to exclude moisture between the inside of the outer plastic coating and the outside of the H or I-pile due to the inconvenient shape of such piling.xe2x80x9d Grosse and Fehr U.S. Pat. No. 3,939,665 does describe why use of metal piling is not good design. Quoting from Grosse and Fehr U.S. Pat. No. 3,939,665, xe2x80x9cIron, as is well known, is not stable when subjected to the usual surface atmospheric conditions. Under such conditions, unprocted iron will oxidize to produce various oxides of iron which are more stable under surface conditions than the uncombined metal. Such oxidation or corrosioin, as is known, is accelerated beneath the surface of bodies of water, especially sea water. Corrosion of metal surfaces is particularly severe in the so-called xe2x80x98splash zone.xe2x80x99 The splash zone is the zone near the surface of the bodies of water, which is alternately exposed to water and air due both to changing level of tides and the like, the breaking of waves, the spray from waves and various other turblences coming in contact with metallic structures.xe2x80x9d
Grosse and Fehr U.S. Pat. No. 3,939,665 does not address, given all the problems associated, why H-piles or I-beam piles are used for piling. Grosse and Fehr U.S. Pat. No. 3,939,665, state that xe2x80x9c(U)nfortunately H-beam and I-beam type piling, while strong and rigid for its weight, has large surface areas which, being made of metal, and usually iron, are subject to oxidation and other corrosive attack when exposed to corrosive environment.xe2x80x9d The reason why H and I-beam piles are frequently used, in spite of corrosion problems, si because of their xe2x80x9c. . . large surface areas . . . xe2x80x9d Piles are xe2x80x9cdrivenxe2x80x9d into a soil matrix. The act of xe2x80x9cdrivingxe2x80x9d the pile causes friction to develop between the soil matrix and the surface of the pile. This is commonly referred to as a pile""s skin-fraction. Pile skin-friction frequently accounts for most or all the physical support the soil-matrix provides. In piling applications where skin-friction is the dominate support mechanism, the xe2x80x9csurface area-to-cross-sectional area ratioxe2x80x9d becomes an important economic issue for a number of reasons. Some of those reasons, but not limited to, are A) transport costs of the pile sections to the installation site. This is a function of how much xe2x80x9csurface-areaxe2x80x9d can be transported at a time. That is, in the case where friction is an important design factor, the more friction developed per length of structural element the lower the overall cost of transportation, and obviously other associated costs, will be. As such, a xe2x80x9croundxe2x80x9d cross-section is less efficient than a xe2x80x9csquarexe2x80x9d which is less efficient than a xe2x80x9ctrianglexe2x80x9d and so on. The more efficient shape for the present invention, in specific applications, would be as a xe2x80x9ccorrugatedxe2x80x9d xe2x80x9csheetxe2x80x9d pile. B) pile driving operations are functions of how long it takes for the pile being xe2x80x9cpushedxe2x80x9d into the soil-matrix to develop the amount of friction to resist the design-loads demanded. The greater the xe2x80x9csurface area-to-cross-sectional area ratioxe2x80x9d the shorter the required length of pile that needs to be placed into the soil-matrix for the required development of friction. C) in extremely xe2x80x9cweakxe2x80x9d soil-matrix conditions, the xe2x80x9cdead-loadxe2x80x9d weight of the pile itself, as a ratio to the unit length of surface area, becomes a design factor. That is, pile-foundations must be designed to carry all design loads including the weight of the pile itself. Increasing the total surface-area available for friction load between pile and soil-matrix while reducing the weight of the pile in question allows for a more overall economic use of materials for the structure intended to be supported by the pile-foundation in question. D) freuqently, a site""s macro-soil-matrix includes layers of xe2x80x9cstrong-soilsxe2x80x9d interlaced with layers of xe2x80x9cweak-soilsxe2x80x9d. Shorter piles which allow full development of design loads without penetrating deeper xe2x80x9cweak-soilxe2x80x9d layers which could lead to foundation instability after installation of a pile foundation. For example, if a pile foundation is driven thru a xe2x80x9cweak-soilxe2x80x9d strata or a series of xe2x80x9cweak-soilxe2x80x9d strata resulting in a xe2x80x9cpuncturexe2x80x9d of a previously water-tight strata, the result may be a xe2x80x9cde-wateringxe2x80x9d of the strata in question which could result in a reducing of load-bearing capacity of said strata. Grosse and Fehr U.S. Pat. No. 3,939,665 would have the pile installer use xe2x80x9c. . . a heavy grease or other petroleum products, applied to the inner surface . . . xe2x80x9d to a pile in -situ. While the state of the art at the time of the Grosse and Fehr U.S. Pat. No. 3,939,665 patent. 1976, may have allowed this practice, present U.S. Environmental Protection Agency regulations make use of such practices more expensive today.
Fox 4,019,301 (Oct. 24,1977) describes xe2x80x9c(A) protective system for concrete, wood and steel piling or other structures subject to corrosion or wear from the action of water. This system includes an encasement sleeve . . . and a filler . . . between the encasement sleeve and the piling.xe2x80x9d xe2x80x9cThe encasement and filler are left permanently on the structure to protect the same from water or other elements, and also to reconstruct worn portions to achieve the original structural integrity of the structures.xe2x80x9d Fox U.S. Pat. No 4,019,301 is a retro-fit invention. It is intended for repair of in-situ piles. Quoting from Fox U.S. Pat. No. 4,019,301, xe2x80x9c. . . and inert sleeve of fiberglass, epoxy, or similar material is formed to fit around the piling and is positioned about the piling at and below the water level. In the space between the encasement sleeve and the piling a filler of epoxy grout or the like is deposited and allowed to set to complete the protective covering for the piling without the need for dewatering procedures.xe2x80x9d As mentioned above, While the state of the art at the time of Fox may have allowed this practice, present U.S. Environmental Protection Agency regulations make use of such practices more expensive today, if in fact legal under present EPA requirements. In addition to potential environmental aspects of the Fox U.S. Pat. No. 4,019,301 invention, the nature of Fox U.S. Pat. No. 4,019,301 may case structural problems. Applicationxe2x80x94of the Fox U.S. Pat. No. 4,019,301 encasement or the Colbert et al U.S. Pat. No. 4,023,374 (May 17, 1977) xe2x80x9csleevexe2x80x9d or the Moore U.S. Pat. No. 4,306,821 (Dec. 22, 1981) xe2x80x9couter circumferential formxe2x80x9d or the Fawley U.S. Pat. No. 5,633,057 (May 27, 1997) xe2x80x9ccomposite reinforcing sleevesxe2x80x9d or Neuner et al. U.S. Pat. No. 5,925,579 (Jul. 2, 1999)xe2x80x94may result in unintended structural loading of the structural element in question. All of the aforementioned inventions add to the diameter of the original structural member. In doing so, the originally intended section-modulus is replaced with a greater section-modulus. In addition, the use of the materials cited in the aforementioned inventions could significantly increase both the structural member""s load carrying capacity but also significantly increase said structural member""s deflection characteristics when under load. By itself, this increase in xe2x80x9cstiffnessxe2x80x9d may not be important in isolation unto said structural member. However, the mentioned structural member is usually a single component of a larger, more complex, structural system. That is, in the case of a wharf, the structural member being only one pile of a number used to support the wharf deck, any increase in stiffness of a single pile will cause loadings to transfer from the less stiff piles to the single stiffer pile. The concentration of load forces can result in significant unintended structural loadings elsewhere in the wharf""s structural system.
Quoting from Fox U.S. Pat. No. 4,019,301 xe2x80x9cit is well known that conventional piles, made of concrete wood or steel, will deteriorate rapidly at the water line, even when reinforced by the use of a combination of these materials.xe2x80x9d Mirmiran et al. U.S. Pat. No. 5,599,599 (Feb. 4, 1997) addresses problems identified by Fox U.S. Pat. No. 4,019,301, as xe2x80x9c(T)he invention has the effect of waterproofing and insulating the exposed concrete columns and piles of infrastructure supports and protecting any steel/metal reinforcing bars and cages in the cement cores from the effects of corrosion.xe2x80x9d Mirmiran U.S. Pat. No. 5,599,599, by encasing; making waterproof, and use of a highly heat insulating material such as FRP, does not address such problems. Mirmiran U.S. Pat. No. 5,599,599 use of FRP pultruted components for shear transfer between the FRP exterior shell and concrete core is questionable due to the smooth surface natural to FRP pulrutions. Finally, Mirmiran U.S. Pat. No. 5,599,599 offered no bonding between the exterior FRP shell and concrete core. Given concrete""s nature to shrink as it ages, any initial shear transferring bond between the FRP shell and concrete core could degrade over time. As noted by Fawley U.S. Pat. No. 5,633,057, xe2x80x9c. . . concrete slurry . . . shrinkage . . . and therefore, there is inadequate load transfer . . . xe2x80x9d i.e. shear.
In each of Mirmiran U.S. Pat. No. 5,599,599 offered embodiments FIG. 1A, FIG. 1B, FIG. 1C, FIG. 1D, FIG. 2A, FIG. 2B, FIG. 3A, FIG. 3B, FIG. 4A and FIG. 4B, quoting from Mirmiran U.S. Pat. No. 5,599,599 xe2x80x9cThe invention consists of hollow FRP shell filled with concrete.xe2x80x9d While Mirmiran U.S. Pat No. 5,599,599 suggests that xe2x80x9c. . . the invention can be used as concrete piles . . . xe2x80x9d, the invention does not address how the FRP shell will encourage skin-friction, nor how in the act of placing the invention into a soil-matrix that it would keep its xe2x80x9cwaterproofingxe2x80x9d. For use as an above ground structural member Mirmiran U.S. Pat. No. 5,599,599 fails to address how to keep fire and/or insulating the exterior shell from damage, both of which directly threaten any Mirmiran U.S. Pat. No. 5,599,599 structure""s structural integrity.
March et al. U.S. Pat. No. 5,658,519 (Aug. 19, 1997) does not address threats of fire, nor skin friction issues, nor economic costs associated with use of plastics. March U.S. Pat. No. 5,658,519 does not address the lack of xe2x80x9cstiffnessxe2x80x9d in handling and driving such as pile. March U.S. Pat. No. 5,658,519 offers no means or methods for field attaching individual sections of pile.
Isley, Jr. U.S. Pat. No. 5,218,810 (Jun. 15, 1993) addresses retro-fitting existing reinforced concrete columns with a composite reinforcement layer on the exterior surface to provide xe2x80x9choopxe2x80x9d strength said column. Isley, Jr. U.S. Pat. No. 5,218,810 requires the composite material to remain of a consistent nature as it is xe2x80x9cwrappedxe2x80x9d around the reinforced concrete column. The present invention""s ability to strategically place composite material(s) on the structural element""s core allows for applications other than columns such as, but not limited to, structural beams. In the specific case of marine foundation piles, the present art of handling piles on job-site requires such piles to act as xe2x80x9cbeamsxe2x80x9d. Isley, Jr. U.S. Pat. No. 5,218,810 only addresses retro-fit applications, not pre-assemble and/or precast and/or off-site manufacturing/fabrication of complete structural elements and thus Isley, Jr. U.S. Pat. No. 5,218,810 does not address problems in the present art of handling pre-assembled and precast structural elements.
It is believed to be advisable to further improve the foundation piles and similar load carrying elements.
Accordingly, it is an object of the present invention to provide a foundation pile which avoids the disadvantages of the prior art.
In keeping with these objects and with others which will become apparent hereinafter, one feature of present invention resides, briefly stated, in a foundation pile which comprises at least one tensioning tendon which is elongated in a direction of elongation, means forming a hollow conduit located around the at least one tendon so that a space remains between the tensioning tendon and the hollow conduit, a structural tubular element located around the hollow conduit and composed of a non-metallic material, a tubular layer of a composite material located around the structural tubular element and connected with the later, and a friction coating applied on an outer surface of the layer of composite material.
When the foundation pile is designed in accordance with the present invention, it does not attempt to apply an outer corrosion resistant coating for the purpose of connecting metal pipes as in the patent to Grosse, and it does not deal with skin-friction problems as in this patent. It avoids the use of metals where corrosion is undesirable and provides a significant wearing surface which negates many of the problems disclosed in the patents to Fox, Moore, Fawle and Neuner. It does not insulate its concrete when concrete is used based on recognition that concrete when allowed to remain moist continues to gain overall strength. It eliminates threats of fire and impact damage in contrast to the patent to Mirmiran, it allows placing individual strips of composite material of different material contents and uses unreinforced concrete core in contrast to the patent to Isley.
The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.